Author Topic: Prop For Heavy Vector 40 (Read 2825 times)

Colin McRae · « **on:** May 22, 2023, 09:45:34 AM »

I was hoping to get a good recommendation on the best prop to try on my Vector 40.

Vitals:
Model is heavy at 61 oz. (I did not build it so did not have control over the final weight)
Wing loading a whopping 16.4 oz/sqft
Running a stock OS 40 LA

I have a lot to learn about props. The APC props in the pic are:
11-4
11.5-4
12-4
12.25-3.75

It is interesting that the 12-4 airfoil is different from the other 3. (Narrower at the hub area)

So, I guess my question is what the best prop (and related ground rpm) might be to use to unleash the best performance for the 40 LA based on others experience on a Vector 40, or other similar size heavy model with a high wing loading. Also, my 40 LA is relatively new and a strong runner. I have also been running Brodak 5% nitro fuel to date (23% oil 50/50 oil mix). I also have some 10% nitro available.

BTW, I also have other props in my box. (MAS, ZOAR wood, BY&O). Thoughts on these as well is welcome.

Thanks in advance.

Allen Eshleman · « **Reply #1 on:** May 22, 2023, 05:47:24 PM »

I don't have a recommendation. I think it's plane particular. Each plane/engine combination has to find its successful combinations.

Testimonial: Today I was flying a Banshee mated to an LA 40 box stock. It has the 6 mm venturi and the O.S. type NVA. I started with a very old Top Flite 11/3. Then I went to a Zinger Pro wood 11/4. Then I used an APC 11/4. It was hands down better for that plane. It seems like I might have found the "ticket" to a good run. I was using 10% nitro with 11 1/2 x 11 1/2 synthetic and castor. I too will be interested to hear the comments of others for your situation.

Dan McEntee · « **Reply #2 on:** May 22, 2023, 06:31:48 PM »

I would shine the airplane up really nice and find a spot to hang it for inspiration and decoration. I'm not above trying to fly a heavy model, and often tell people that if you can get a heavy model trimmed out to fly a pattern well, you can do the same to almost any airplane. ALMOST and airplane. The vector isn't all that big, and most of the arfs that I have seen people finish off seem to get them in at 45 to 50 ounces, and the 50 ounce weight might be the limit I think. I don't think I have ever seen any model with any brand .40 in it fly a 60 plus ounce airplane unless it was a tuned pipe VF.40. The closest thing I have to relate it to is a Legacy .40 that weighs 60 ounces and uses every bit of power that a Brian Gardner LA.46 can muster up. I run an APC 12.25-3.75 on that. The prop won't make much of a difference, but I think the best hope you have is the APC 11.5-4 and spin that puppy up.
Good luck with the effort,
Dan McEntee

Colin McRae · « **Reply #3 on:** May 22, 2023, 10:18:05 PM »

Thx for the input, but I will keep experimenting. Yes, it is a very heavy model, but other heavy models can fly well. I like the 40 LA and will continue try different options and trim, fuel nitro, etc. At the end of the day, I do have a 46LA available, but I am not convinced as yet that the 40 will not work.

Whoever build the model did a very professional job, but unfortunately it ended up heavy.

Dave Hull · « **Reply #4 on:** May 22, 2023, 11:04:04 PM »

Nice looking plane, for sure.

How are the controls set up? One-to-one on the flaps?

Dave

Colin McRae · « **Reply #5 on:** May 23, 2023, 09:46:51 AM »

Yes, 1-1 on the flaps. Model came that way. I would have to cut into the model to change.

The AMA number on the wing is 679310. Whoever that was build a beautiful model.

john e. holliday · « **Reply #6 on:** May 23, 2023, 10:17:20 AM »

I know it is a lot of work. I have a plane that is about ther same size. I flew it for several years trying to trim it. Then one day instead of starting a new I pulled this plane off the hook and removed everything. Then started removing the covering. It was fished using the composite coving I have been doing on planes. Yes it was a mess getting the finish off the plane. The doc paper was stuck good. I recovered with just Super MonoKote. The plane came out a good 6 ounces lighter. As soon as the knees say it is okay I will fly it. But, I also need a way to get to the field. Family don't trust me driving.

Colin McRae · « **Reply #7 on:** May 23, 2023, 10:33:54 AM »

Quote from: john e. holliday on May 23, 2023, 10:17:20 AM

I know it is a lot of work. I have a plane that is about ther same size. I flew it for several years trying to trim it. Then one day instead of starting a new I pulled this plane off the hook and removed everything. Then started removing the covering. It was fished using the composite coving I have been doing on planes. Yes it was a mess getting the finish off the plane. The doc paper was stuck good. I recovered with just Super MonoKote. The plane came out a good 6 ounces lighter. As soon as the knees say it is okay I will fly it. But, I also need a way to get to the field. Family don't trust me driving.

Thx Doc.

I am nowhere near any type of competition level flying. Mostly sport, and slowly working away on the pattern. But use other practice models for obvious reasons. I have been sport-flying the Vector to learn it and continue the trimming process.

I still consider myself a rookie builder so won't be ripping the Vector apart. I will just live w/ a heavy model and just try to optimize what it can do as is.

Brett Buck · « **Reply #8 on:** May 23, 2023, 11:28:28 AM »

Quote from: Colin McRae on May 22, 2023, 10:18:05 PM

Thx for the input, but I will keep experimenting. Yes, it is a very heavy model, but other heavy models can fly well. I like the 40 LA and will continue try different options and trim, fuel nitro, etc. At the end of the day, I do have a 46LA available, but I am not convinced as yet that the 40 will not work.

That is really pushing the limits, however. But it is far from the worst example I have seen.

Of the props you suggest, I would start with the 11.5-4 APC and a *stock* 46LA. I flew my 64 ounce (after a 2-day rebuild) Imitation XL at the Lubbock NATs with the original narrow-blade 11.5-4, you can probably only get the wide-blade version now. That was with a piped 40VF. which tells you how hard you are going to ahve to run your 46LA.

High RPM and low pitch is the solution to the weight problem. To give yourself the best chance, expect to have to really crank up the engine, and reduce the pitch as necessary to get the speed down. The 12.25-3.75 will probably be even better from a propulsion standpoint but that is one big heavy prop to be putting on the little Vector, no more fin or side area than you have.

Brett

Colin McRae · « **Reply #9 on:** May 23, 2023, 03:18:28 PM »

Quote from: Brett Buck on May 23, 2023, 11:28:28 AM

That is really pushing the limits, however. But it is far from the worst example I have seen.

Of the props you suggest, I would start with the 11.5-4 APC and a *stock* 46LA. I flew my 64 ounce (after a 2-day rebuild) Imitation XL at the Lubbock NATs with the original narrow-blade 11.5-4, you can probably only get the wide-blade version now. That was with a piped 40VF. which tells you how hard you are going to ahve to run your 46LA.

High RPM and low pitch is the solution to the weight problem. To give yourself the best chance, expect to have to really crank up the engine, and reduce the pitch as necessary to get the speed down. The 12.25-3.75 will probably be even better from a propulsion standpoint but that is one big heavy prop to be putting on the little Vector, no more fin or side area than you have.

Brett

Thanks Brett
On Sunday I did run the 11.5-4 APC (wide version) w/ the 40LA. 60' 018 lines. It was doing under 5 sec laps so way to fast w/ hard pull. So, lots of issues I need to tame down.

The 12-4 APC I have has the more the conventional sport prop airfoil. Narrow near the hub. I will try that next. And keep experimenting.

I also have never run a 3-blade prop. Any value added and is this an option?

Brett Buck · « **Reply #10 on:** May 23, 2023, 05:11:55 PM »

Quote from: Colin McRae on May 23, 2023, 03:18:28 PM

Thanks Brett
On Sunday I did run the 11.5-4 APC (wide version) w/ the 40LA. 60' 018 lines. It was doing under 5 sec laps so way to fast w/ hard pull. So, lots of issues I need to tame down.

The 12-4 APC I have has the more the conventional sport prop airfoil. Narrow near the hub. I will try that next. And keep experimenting.

I also have never run a 3-blade prop. Any value added and is this an option?

The problem with that is when you try to slow it down too much, and it starts stalling. The reason to use low-pitched props is to try to narrow the speed range in flight, heavy airplanes have more induced drag, and need more angle-of-attack. so they slow down much more in the corners (due to the drag) and this also requires more AoA - so they have a strong tendency to slow down and stall.

Low pitched props spun by very powerful engines resist this speed change much better than a 4-2 break engine with a high-pitched prop. So you should not have to fly it as fast in level flight just to give it enough for the corners. That is the key to modern stunt plane performance and why what used to be considered "grossly overweight" airplanes in the ancient era (before 1988 or so) are routinely winning national championships - in fact there may have only been one NATs winner in the last that met the old "12 ounces square foot MAX!" rule.

So, you best bet is to crank it up, control the speed with pitch, and fly it as fast as you can. See how it goes, we have a few other tricks (like PJ's "vortex generators") that might help you if you are close to the edge.

Brett

Colin McRae · « **Reply #11 on:** May 23, 2023, 06:32:11 PM »

Quote from: Brett Buck on May 23, 2023, 05:11:55 PM

The problem with that is when you try to slow it down too much, and it starts stalling. The reason to use low-pitched props is to try to narrow the speed range in flight, heavy airplanes have more induced drag, and need more angle-of-attack. so they slow down much more in the corners (due to the drag) and this also requires more AoA - so they have a strong tendency to slow down and stall.

Low pitched props spun by very powerful engines resist this speed change much better than a 4-2 break engine with a high-pitched prop. So you should not have to fly it as fast in level flight just to give it enough for the corners. That is the key to modern stunt plane performance and why what used to be considered "grossly overweight" airplanes in the ancient era (before 1988 or so) are routinely winning national championships - in fact there may have only been one NATs winner in the last that met the old "12 ounces square foot MAX!" rule.

So, you best bet is to crank it up, control the speed with pitch, and fly it as fast as you can. See how it goes, we have a few other tricks (like PJ's "vortex generators") that might help you if you are close to the edge.

Brett

Thx Brett

BTW, the OS 40 LA I am running is 'stock' except for the remote NVA. Due to the Vector cowl, I am using an OS spec Enya type front NVA that I got from Shtterman (Bobby Brooks). Engine runs strong. I do have a 46LA in my back pocket.

And the primary reason I am giving the 40LA its chance to succeed is that it is heavier than the 46 LA. The model as built is very tail heavy. I am currently using a 3 oz heavy brass spinner nut just to get it close to a good CG point. So, lots of issues for sure!

Dan McEntee · « **Reply #12 on:** May 25, 2023, 03:15:08 PM »

Quote from: Colin McRae on May 23, 2023, 06:32:11 PM

Thx Brett

BTW, the OS 40 LA I am running is 'stock' except for the remote NVA. Due to the Vector cowl, I am using an OS spec Enya type front NVA that I got from Shtterman (Bobby Brooks). Engine runs strong. I do have a 46LA in my back pocket.

And the primary reason I am giving the 40LA its chance to succeed is that it is heavier than the 46 LA. The model as built is very tail heavy. I am currently using a 3 oz heavy brass spinner nut just to get it close to a good CG point. So, lots of issues for sure!

I would give serious consideration to installing that 3 ounces of nose weight and mounting it in lead permanently in the nose and get it off the shaft of the engine. Those are OK for a quick few flights to test balance and such, and I don't know for sure if it affects how the engines runs or not, but I have seen engines run like this suddenly break crank shafts. 3 ounces is a LOT of weight up there bouncing around.
Type at you later,
Dan McEntee

Colin McRae · « **Reply #13 on:** May 25, 2023, 05:47:27 PM »

Quote from: Dan McEntee on May 25, 2023, 03:15:08 PM

I would give serious consideration to installing that 3 ounces of nose weight and mounting it in lead permanently in the nose and get it off the shaft of the engine. Those are OK for a quick few flights to test balance and such, and I don't know for sure if it affects how the engines runs or not, but I have seen engines run like this suddenly break crank shafts. 3 ounces is a LOT of weight up there bouncing around.
Type at you later,
Dan McEntee

Thanks, Dan, for the heads up. I realize the 3.25 oz heavy brass spinner nut hangs off the end of the shaft. I have always wondered if it would eventually damage the engine bearing, or something even worse!

But the 3.25 oz nut is as far forward as it can be. If I bury weight in the cowl area it would have to be more than 3.25 oz (maybe 4-5 oz) to get the same CG balance effect. But I am trying to 'lower' the overall weight of the already heavy 60+ oz model. A real dilemma !!

I would appreciate input from others concerning the 3.25 oz heavy brass spinner nut on an OS 40 LA 1/4-28 shaft. Am I playing with fire? Not good for the bearing? Risk of damaging the shaft? Do others have direct experience I can learn from?

Another way to look at it is to use say a 1 oz? spinner nut to get as much weight forward as possible. Then the rest of the weight in the cowl area. So, on a 40 LA shaft, how much weight can go on the end of the shaft without compromising engine function or longevity?

Thanks again for all for the help.

Brett Buck · « **Reply #14 on:** May 25, 2023, 09:08:11 PM »

Quote from: Colin McRae on May 25, 2023, 05:47:27 PM

Thanks, Dan, for the heads up. I realize the 3.25 oz heavy brass spinner nut hangs off the end of the shaft. I have always wondered if it would eventually damage the engine bearing, or something even worse!

But the 3.25 oz nut is as far forward as it can be. If I bury weight in the cowl area it would have to be more than 3.25 oz (maybe 4-5 oz) to get the same CG balance effect. But I am trying to 'lower' the overall weight of the already heavy 60+ oz model. A real dilemma !!

For this purpose, it won't do anything significant, just leave it for now.

Brett

Steve Helmick · « **Reply #15 on:** July 02, 2023, 04:51:54 PM »

I would put a nice regular spinner on the .40LA, cut off the leadouts and then hang the plane on the shop wall. Seriously, I've flown enough overweight stunters already, and they were all bad. Nothing you can do about it being 10 oz overweight, and it sounds like your Vector 40 will be more like 15 oz overweight by the time you get the CG right.

Steve

Colin McRae · « **Reply #16 on:** July 03, 2023, 12:55:25 PM »

I appreciate the suggestion of 'just hang it up and don't fly it', but I don't compete and fly mostly sport. But I am working away at the pattern just to learn and get comfortable with all the different maneuvers.

I purchased the Vector already built and for a song, and it is a beautifully built model. One thing I have learned first-hand is how much covering and paint can weigh if not careful. Not sure what the original builder was thinking.

I look at this overall experience as another learning possibility for me. This model, with its high wing loading just might never be able to do the full pattern properly. Time will tell.

In the meantime, it does fly reasonably well, and it just might end up being one of my models that I fly for sport. Just need to keep away from certain maneuvers.

Motorman · « **Reply #17 on:** July 03, 2023, 01:48:42 PM »

A really good prop for that would be those 11x4.5 gray plastic TT props Randy Smith had made special. I've got them on 3-4 planes that size, good blade area and good drive.

The thing about the B plane is that if you fly it allot you'll become acclimated to it's quirks. Then when you get a good plane you'll have to go through a re-adjustment period. If you want to be a competition flyer you should get the best plane you can out there so your time is well spent. Only fly B planes when it's super windy and hope they crash to free up space in the shop.

If you're just sport flying then all apologies. I would get .015" lines 63' handle to thrust line and go for a 5.2 lap time. Maintain large radius turns and keep your momentum up, no sharp moves that would stall the wing. Fly the pattern perfectly with no glitches is your best bet.

For the tail weight problem, have you tried a wider spacing on the handle and set the elevator horn to the longest lenght? If you've got those two things maxed out and it's still too sensitive then nose weight might be the only solution but sometimes you can fly it enough to get smooth with it.

MM

Colin McRae · « **Reply #18 on:** December 14, 2023, 02:50:44 PM »

I was finally able to get in a few laps with the Vector today. I have been experimenting with different props looking at thrust and speed. I also am trying out longer lines as 64'.

Following Brett's basic suggestion for a typical heavy model (large prop, low pitch, spinning fast), today I tried a BY&O wood 12-3 and the best ground rpm I could achieve. (BY&O is the only prop I could find with a 3 pitch.) I was able to get right at 10,000 rpm on the ground. The engine did speed up a little once in the air.

So far, this prop seems to be best for my heavy Vector with the 46LA engine. Lap time around 5 sec (64' lines) and the engine/prop combo seemed to provide adequate power, even overhead,

This is probably the best it will get for this particular model.

Dan McEntee · « **Reply #19 on:** December 14, 2023, 10:22:34 PM »

Quote from: Colin McRae on December 14, 2023, 02:50:44 PM

I was finally able to get in a few laps with the Vector today. I have been experimenting with different props looking at thrust and speed. I also am trying out longer lines as 64'.

Following Brett's basic suggestion for a typical heavy model (large prop, low pitch, spinning fast), today I tried a BY&O wood 12-3 and the best ground rpm I could achieve. (BY&O is the only prop I could find with a 3 pitch.) I was able to get right at 10,000 rpm on the ground. The engine did speed up a little once in the air.

So far, this prop seems to be best for my heavy Vector with the 46LA engine. Lap time around 5 sec (64' lines) and the engine/prop combo seemed to provide adequate power, even overhead,

This is probably the best it will get for this particular model.

As you experiment with different pitch, keep blade area in mind also. The BY&O paddle blade props work better at lower RPM. What you are trying is kind against what you are trying to achieve. Now that you have these results in you files, find some other narrow blade 12-3 props, or if you have to, repitch a 12-4 down to 12-3. Repitching props is a good skill to know. When you get one you like, out of say an old Zinger, or Rev-up 12-4 or 12-5, I think you will find that it will rev more with a narrower blade. That extra blade area is like hauling around and extra blade. You might try narrowing down a BY&O 12-3 a little at a time, rebalance it and fly it and see what you get. There is lots to observe and learn from this endeavor. It's like the late great Yogi Berra once said, " You can observe a lot just by watchin'."
Type at you later,
Dan McEntee

PS to Add; You might want to grab a bag of those Rev-Up drone props that BYU has for sale in the classifieds. I have found these to be VERY adaptable to different diameters, pitch, and blade shape. You might find cutting one down to a 11.5 or or so may get you what you need. But off the tips 1/8" at a time, rebalance and fly several flights at different needle settings. You can always cut more off the tip but you can't put it back on, so that's why you do it a little at a time and observe the results. When you have gone too far, you will know.

Dennis Toth · « **Reply #20 on:** December 15, 2023, 08:29:43 AM »

Colin,
There are a few things that might help. Go with the 46 as it is more power, more power more prop more pulling power. Second, put on a smaller tail wheel will reduce the amount of nose weight (I have use 3/8" diameter to get weight out the tail). I don't know if you have any larger engine but stuff in the biggest one you can to reduce the added nose weight. If you need to add nose weight you could get some lead shot and put them in the backplate cavity with some clay to secure them (could melt it into the backplate) add a cover plate that uses the backplate bolts to hold it from brass or tin to keep the weight from flopping around. Keep working with the props, maybe try a Master Airscrew 3 blade (https://www.masterairscrew.com/collections/3-blade/electric-motors?filter.p.m.custom.diameter=11.0) they are underpitch by about 1" so the 11x6 is like an 11x5. They can also be heat pitched to whatever you want.

Best, DennisT

Colin McRae · « **Reply #21 on:** December 15, 2023, 08:49:28 AM »

Quote from: Dan McEntee on December 14, 2023, 10:22:34 PM

As you experiment with different pitch, keep blade area in mind also. The BY&O paddle blade props work better at lower RPM. What you are trying is kind against what you are trying to achieve. Now that you have these results in you files, find some other narrow blade 12-3 props, or if you have to, repitch a 12-4 down to 12-3. Repitching props is a good skill to know. When you get one you like, out of say an old Zinger, or Rev-up 12-4 or 12-5, I think you will find that it will rev more with a narrower blade. That extra blade area is like hauling around and extra blade. You might try narrowing down a BY&O 12-3 a little at a time, rebalance it and fly it and see what you get. There is lots to observe and learn from this endeavor. It's like the late great Yogi Berra once said, " You can observe a lot just by watchin'."
Type at you later,
Dan McEntee

PS to Add; You might want to grab a bag of those Rev-Up drone props that BYU has for sale in the classifieds. I have found these to be VERY adaptable to different diameters, pitch, and blade shape. You might find cutting one down to a 11.5 or or so may get you what you need. But off the tips 1/8" at a time, rebalance and fly several flights at different needle settings. You can always cut more off the tip but you can't put it back on, so that's why you do it a little at a time and observe the results. When you have gone too far, you will know.

"What you are trying is kind against what you are trying to achieve."

Sorry Dan but I'm not sure I understand your comment. I have tried various 11" and 12" 4-pitch props, both narrow and wide versions, and the wide-blade 12-3 BYO seems to pull the Vector better while keeping the speed in check. And I know the longer 64' lines is also contributing to a more reasonable lap time. My specific experience is the prop pitch is far and away the predominant factor affecting the overall performance with my heavy Vector.

I am a relative rookie to this hobby and don't have the skills or tools to re-pitch a prop. So, I go with what I can find commercially. A 3 vs 4 pitch is a big change (compared to 5 vs 6 for instance). And so far, BYO is the only 12" 3-pitch prop I can find.

I am also a long way off from being able to perform all pattern maneuvers. I only recently started learning the OH8. I also have the luxury of flying with an expert buddy and I will also get his opinion once he flies my model.

Dan McEntee · « **Reply #22 on:** December 15, 2023, 05:51:15 PM »

Quote from: Colin McRae on December 15, 2023, 08:49:28 AM

"What you are trying is kind against what you are trying to achieve."

Sorry Dan but I'm not sure I understand your comment. I have tried various 11" and 12" 4-pitch props, both narrow and wide versions, and the wide-blade 12-3 BYO seems to pull the Vector better while keeping the speed in check. And I know the longer 64' lines is also contributing to a more reasonable lap time. My specific experience is the prop pitch is far and away the predominant factor affecting the overall performance with my heavy Vector.

I am a relative rookie to this hobby and don't have the skills or tools to re-pitch a prop. So, I go with what I can find commercially. A 3 vs 4 pitch is a big change (compared to 5 vs 6 for instance). And so far, BYO is the only 12" 3-pitch prop I can find.

I am also a long way off from being able to perform all pattern maneuvers. I only recently started learning the OH8. I also have the luxury of flying with an expert buddy and I will also get his opinion once he flies my model.

Well, you said you went to a 3" pitch looking for more RPM in order to make more thrust. With the BY& O, you probably have about half again more blade area than what you were using, maybe more, and that tends to offset the reduced pitch that would have freed up the engine. The BY&O prop is a good prop. It's origins go back to the ignition days when they were just called Y&O for Yates and Orwick. Those names are familiar to old timers. They produced the props up into the 60s' I think, maybe later. I have collected several in many sizes that are Y&O. Then when the classic/vintage movement started , and gentleman named Clarence Bull (Bule??) acquired the tooling and added his initial to the from of the name, creating BY&O. Clarence passed away and John Brodak picked up the line and improved some things with the help of Jim Hunt, Bob's Dad, and then Brodak has added some to the line. For the most part, they are primarily paddle blade shaped because they were developed at a time when most engines ran 8 to 9,000 RPM, so more blade area for more thrust. When you get up to that 10,000rpm range they can add a lot of load to the engine. You said you barely got to 10,000. A modern 11 to 12-4 will push 11,000 at least on a LA.46. So in short, you don't want to just take pitch itself as gospel and all props will perform the same at that pitch. Blade shape is important , especially the tip shape sometimes. I suggest saving your money and buy a good pitch gauge as you accumulate a prop inventory. With the way things are, there are fewer and fewer off the shelf wood props available. If you learn to rework props, that opens up a lot of options for you. Prather pitch gauges are out there and can bring a high price but deals can be found. Jim Lee carried a pitch gauge that will also measure left hand props. The pitch gauge, a balancer set up, a pair of dial calipers, and a good selection of sanding blocks are all you need. The price of 3 or 4 carbon fiber props will easily get you there and you will always have it. The Thunder Tiger 11-4.5 that everyone likes for the LA.46 isn't in production any long, I think, but may be some stock out there in various places. No matter, because if you can cut and carve a wooden copy of the same prop, it will work just as good and be about 3/4 ounces lighter!! I have been experimenting with this most of this past summer and have had really satisfying results!!
Type at you later,
Dan McEntee

Alan Buck · « **Reply #23 on:** December 16, 2023, 08:15:06 AM »

Colin if you need 3ozs of nose weight I would go for
a larger engine like a super tigre 51 more power and
the weight same

Colin McRae · « **Reply #24 on:** December 16, 2023, 10:55:39 AM »

This is interesting, the pic shows a 12-4 BY&O (top) and 12-3 BY&O (bottom), both from Brodak. The 3 pitch airfoil is significantly wider than the 4 pitch.

The 12-4 is a similar shape to say a MAS or XOAR.

Might anyone know the history of the designs? Maybe the 12-3 wide airfoil is from the original BYO design, and Brodak has an update for the 12-4, more conventional airfoil maybe.

In any event, the wide 12-3 along with OS 46LA sure does pull the model well without being overly fast.

David_Ruff · « **Reply #25 on:** December 16, 2023, 11:59:14 AM »

Mr. Urtnowsky calls it "trimming" your plane.

Colin McRae · « **Reply #26 on:** December 16, 2023, 12:18:21 PM »

Quote from: David_Ruff on December 16, 2023, 11:59:14 AM

Mr. Urtnowsky calls it "trimming" your plane.

Exactly what I am involved with !!

Dan McEntee · « **Reply #27 on:** December 16, 2023, 10:22:24 PM »

Quote from: Colin McRae on December 16, 2023, 10:55:39 AM

This is interesting, the pic shows a 12-4 BY&O (top) and 12-3 BY&O (bottom), both from Brodak. The 3 pitch airfoil is significantly wider than the 4 pitch.

The 12-4 is a similar shape to say a MAS or XOAR.

Might anyone know the history of the designs? Maybe the 12-3 wide airfoil is from the original BYO design, and Brodak has an update for the 12-4, more conventional airfoil maybe.

In any event, the wide 12-3 along with OS 46LA sure does pull the model well without being overly fast.

This is exactly what i was trying to convey to you. The bottom prop is the 12-3 BY&O and it is just like the originals. The 12-4 is a newer, more modern blade shape. They may offer that prop in the older shape also. The 13-6 BY&O that Brodak makes looks like the top prop pictured, the 12-4. It's a pretty darn good prop also for ST.60's. Again, an interesting experiment would be to depitch that 12-4 down to a 12-3 and see what that will turn up to. I would bet a dollar against a dozen donuts it would rev higher than 10,000rpm and get more into the power band of that engine, and at the same time make more thrust. The best way to find out is to just do it and fly it. If it doesn't work, you can put it back. you have all the data and feedback from the wide blade prop to work against now You might be surprised to see what 200 to 300 more RPM might do, and you might even get to 10,500 and still have some needle left. It is worth it to try , even if you have to get some one to help you repitch the prop It will not hurt it at all.
One thing about owning and learning to use a prop pitch gauge. Once you have one , it is a real eye opener some times into what the actual pitch of the props you are buy really are!! There is a real outside chance that the BY&O 12-3 isn't really a 3" pitch. Wood props sometimes change if they are left to sit for a long time. The wood changes moisture content and the wood relaxes. it gets stress built up and then relieved during the machining , shaping and sanding processes, and then it sit in a box or a bin until it's purchased, or if you bought it used, it sat in the previous owners garage with temps and humidity going up and down and that causes the grain to change a bit. It doesn't hurt the prop any, but it sure helps you to know exactly what it is when you are trying to get your best run. And with trying to trim out a heavy airplane like you are doing, you need every little bit of performance you can get out of the engine and propeller.
Type at you later, and HAPPY HOLIDAYS!!
Dan McEntee

Colin McRae · « **Reply #28 on:** December 17, 2023, 09:12:09 AM »

Quote from: Dan McEntee on December 16, 2023, 10:22:24 PM

This is exactly what i was trying to convey to you. The bottom prop is the 12-3 BY&O and it is just like the originals. The 12-4 is a newer, more modern blade shape. They may offer that prop in the older shape also. The 13-6 BY&O that Brodak makes looks like the top prop pictured, the 12-4. It's a pretty darn good prop also for ST.60's. Again, an interesting experiment would be to depitch that 12-4 down to a 12-3 and see what that will turn up to. I would bet a dollar against a dozen donuts it would rev higher than 10,000rpm and get more into the power band of that engine, and at the same time make more thrust. The best way to find out is to just do it and fly it. If it doesn't work, you can put it back. you have all the data and feedback from the wide blade prop to work against now You might be surprised to see what 200 to 300 more RPM might do, and you might even get to 10,500 and still have some needle left. It is worth it to try , even if you have to get some one to help you repitch the prop It will not hurt it at all.
One thing about owning and learning to use a prop pitch gauge. Once you have one , it is a real eye opener some times into what the actual pitch of the props you are buy really are!! There is a real outside chance that the BY&O 12-3 isn't really a 3" pitch. Wood props sometimes change if they are left to sit for a long time. The wood changes moisture content and the wood relaxes. it gets stress built up and then relieved during the machining , shaping and sanding processes, and then it sit in a box or a bin until it's purchased, or if you bought it used, it sat in the previous owners garage with temps and humidity going up and down and that causes the grain to change a bit. It doesn't hurt the prop any, but it sure helps you to know exactly what it is when you are trying to get your best run. And with trying to trim out a heavy airplane like you are doing, you need every little bit of performance you can get out of the engine and propeller.
Type at you later, and HAPPY HOLIDAYS!!
Dan McEntee

Thanks Dan, I really appreciate all of your comments and insight.

I have not tried the narrow 12-4 BYO as yet and will do so to compare. I don't have a graph of the power/torque curve for the 46LA, but I have seen one for the 40FP (and I know they will not be the same). But if you look at the 40FP, the power peaks around 11,000, but is pretty flat between 10,000-12,000, so good power in that entire rpm range.

And when I adjust the needle for each prop experiment, I find peak rpm, then open the needle maybe 30 deg for the launch rpm to get a healthy wet 2-stroke. The engine does speed up a bit once in the air so the prop speed for the wide 12-3 is >10,000 rpm during flight without being too lean.

All I can say, so far, is that the wide 12-3 BYO at around 10,000 on the ground pulled the heavy model well while keeping the speed reasonable. And the longer 64' lines also helped overall with lap speed management.

Colin McRae · « **Reply #29 on:** December 21, 2023, 08:47:19 AM »

Quote from: Colin McRae on December 16, 2023, 10:55:39 AM

This is interesting, the pic shows a 12-4 BY&O (top) and 12-3 BY&O (bottom), both from Brodak. The 3 pitch airfoil is significantly wider than the 4 pitch.

The 12-4 is a similar shape to say a MAS or XOAR.

Might anyone know the history of the designs? Maybe the 12-3 wide airfoil is from the original BYO design, and Brodak has an update for the 12-4, more conventional airfoil maybe.

In any event, the wide 12-3 along with OS 46LA sure does pull the model well without being overly fast.

I found out more info on the Brodak BY&O 12-3 wide prop.

Brodak was having the BY&O props fabricated in China a few years back, and they had the wide blade design. Since they still have a lot of the wide version 12-3's in stock, that is all they are offering. Not available in a narrower airfoil design.